Caster assemblies are generally well known in the art for carrying out easy movement of an article. These assemblies are provided on a wide variety of articles that are moveable by rolling, including chairs and other furniture (desks, tables, sofas, beds, etc.), stands for medical equipment and other instrumentation, cabinets, work surfaces, dollies, and the like. In addition, other end pieces including glides and adjusters for longitudinal adjustment are also attachable to a wide variety of articles.
Chairs, including industrial and office chairs, as well as other articles of furniture, are often produced with tubular metal legs as need and buyer demand dictates. The tubular legs are typically constructed of metal tubing stock which has an inside diameter that may be substantially larger than the stem of a caster or other end piece that is being coupled thereto and therefore an insert must be installed in the tubular metal leg which forms a socket for coupling the stem of the caster (or other end piece) to the leg member. Alternatively, the leg member may comprise a hard plastic resin material depending on the configuration of the article. As used herein the term “leg member” is intended to cover the legs of chairs, stools and other seats as well as diverse furniture articles (desks, tables, sofas, beds, etc.) having legs that may desirably require casters, glides or adjusters.
As shown in FIG. 1, a caster assembly may comprise caster 10 comprising a wheel 12 that is rotationally coupled to a caster frame 14. The caster frame 14 is coupled to a stem 20 which allows the caster assembly to be rotationally attached to a tubular leg member 30 such that the wheel 12 is free to pivot relative to the tubular leg member. Additionally, while the assembly is shown as it relates to a caster, other end pieces, including glides and adjusters, can be attached to the tubular leg member 30 in a similar manner. Typical assemblies are described, for example, in U.S. Pat. No. 2,294,807 to Schulz, U.S. Pat. No. 2,173,950 to Parkhill, and U.S. Pat. No. 3,128,495 to Tooth.
As shown in FIG. 1, the stem 20 is inserted into an opening in the socket 25 in which the stem 20 is to be retained. The socket 25 is pressfit or otherwise retained in a cavity within the leg member 30 (or other similar leg member) dimensioned to receive the socket.
The socket 25 for coupling the caster to the leg member is typically constructed of a hard plastic resin, such as Nylon-6. One of the problems with the use of these hard plastic resins is that the socket 25 is subjected to stresses to the socket from the caster caused by the movement of the caster during its normal use. These stresses can cause the socket to become worn and loosen within the leg member 30. If this occurs, the socket can eventually dislodge, along with the caster or other end piece, from the tubular leg member making it difficult or virtually impossible to retain the caster within the leg member.
Thus, there remains a need in the art for an improved device for securing casters and/or other end pieces to articles of furniture and the like.